| 1. |
- Engström, Johanna, 1981-
(författare)
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Ice, wood and rocks : regulating elements in riverine ecosystems
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Riparian ecosystems are of great importance in the landscape, connecting landscape elements longitudinally and laterally and often encompassing sharp environmental gradients in ecological processes and communities. They are influenced by fluvial disturbances such as flooding, erosion and sediment deposition, which create dynamic and spatially heterogeneous habitats that support a high diversity of species. Riverine ecosystems belong among the world’s most threatened systems. In rivers throughout the world, human alterations to fluvial disturbance regimes have resulted in degraded ecosystems and species loss. For example, in Sweden, watercourses of all sizes have been channelized to facilitate timber floating, but in the last 10–20 years the impacts in some of the affected rivers have been reduced by restoration actions. The objectives of this thesis are to evaluate how riverine ecosystems in general, with specific focus on riparian communities, are affected by (1) restoration of channelized reaches by boulder replacement, (2) ice formation, and (3) restoration of in-stream wood abundance in the stream channel. Objective (1) was assessed by quantifying the retention of plant propagules in channelized and restored stream reaches and by evaluating effects on riparian plant and bryophyte communities in disconnected and re-opened side channels. Retention of plant propagule mimics was highest at low flows and in sites where boulders and large wood had been replaced into the channel. Propagules are however unlikely to establish unless they can be further dispersed during subsequent spring high flows to higher riparian elevations suitable for establishment. Thus, immigration to new suitable sites may occur stepwise. Our study demonstrates that restoration of channel complexity through replacement of boulders and wood can enhance retention of plant propagules, but also highlights the importance of understanding how restoration effects vary with flow. We detected no differences in riparian diversity between re-opened and disconnected side channels, but we did observe significant differences in species composition of both vascular plant and bryophyte communities. Disconnected sites had more floodplain species, whereas restored sites had more species characteristic of upland forest. This suggests that the reopening of side channels resulted in increased water levels, resulting in new riparian zones developing in former upland areas, but that the characteristic floodplain communities have not had time to develop in response to the restored fluvial regime. Objective (2) was approached by evaluating the effect of both natural anchor ice formation and experimentally created ice in the riparian zone. Riparian plant species richness and evenness proved to be higher in plots affected by anchor ice. Plants with their over-wintering organs above the ice sheet suffered from the treatment but the overall species richness increased in ice-treated plots. Objective (3) was evaluated by studying wood recruitment and movement, channel hydraulics, propagule retention and fish abundance in streams restored with large wood. Only one stream experienced reduced velocities after large wood addition. The large size and reduced velocity were probably also the reasons why this stream proved to be the best one in trapping natural, drifting wood. Increased retention and decreased mechanical fragmentation in large wood sites will lead to decreased loss of detritus from the site and therefore higher availability of coarse particulate organic matter which can result in more species rich shredder communities. Our study did not show that the occurrence of large wood had an important role in controlling density or biomass of brown trout.
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| 2. |
- Myrstener, Maria, 1989-
(författare)
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The role of nutrients for stream ecosystem function in Arctic landscapes : drivers of productivity under environmental change
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Arctic and sub-Arctic freshwaters are currently experiencing substantial ecosystem changes due to the effects of global warming. Global warming effects on these freshwaters include increasing water temperatures, altered hydrological patterns, shifts in riparian vegetation and changes in the export of nutrients and carbon from soils. How these alterations to the physical and chemical hab-itat will affect stream ecosystem functioning largely depends on the responses by autotrophic pro-ducers and heterotrophic primary consumers. In this thesis, I explore how key stream ecosystem processes such as metabolic rates and nutrient cycling vary as a function of climate and landscape drivers, particularly light, temperature, and nutrient and carbon availability. To do this I leveraged natural gradients in vegetation, altitude, disturbance, and precipitation throughout the year in northern Sweden, as well as long- and short-term manipulations of nutrient availability. I also synthesized nutrient limitation data from lakes and streams to more holistically assess the re-sponses of boreal to Arctic freshwaters to changes in nutrients and climate variables. I found that nutrient availability, and especially nitrogen (N), is a main driver of spatial and temporal patterns of biofilm productivity, whole system metabolic rates, and short term N uptake in Arctic and sub-Arctic streams. I also show the importance of light and temperature constraints during early spring and late autumn, which set the limit for the aquatic growing season and annual productivity pat-terns. I present a first comparison of combined drivers of lake and stream responses to nutrient addition, which points to a shared importance of N and phosphorus (P) rather than light or tem-perature in driving the magnitude of nutrient limitation across these systems. Ultimately, I pro-pose that across large ranges in habitat variables, widespread nutrient limitation of Arctic fresh-waters constrain other climate change effects on ecosystem functions. The results presented in this thesis will promote better predictions of climate change effects on Boreal to Arctic stream ecosystem functioning.
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| 3. |
- Nilsson, Christer, et al.
(författare)
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Ecological Restoration as a Means of Managing Inland Flood Hazards
- 2018
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Ingår i: BioScience. - : Oxford University Press. - 0006-3568 .- 1525-3244. ; 68:2, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- Many streams and rivers experience major floods. Historically, human societies have responded to such floods by moving away from them or by abating them, the latter with large negative impacts on stream and river ecology. Societies are currently implementing a strategy of "living with floods,"which may involve ecological restoration. It further involves flood mapping, forecasting, and warning systems. We evaluate 14 different stream-and river-restoration measures, which differ in their capacity to modify water retention and runoff. We discuss these restoration measures in the light of predicted changes in climate and flooding and discuss future restoration needs. We focus on the Nordic countries, where substantial changes in the water cycle are foreseen. We conclude that sustainable solutions require researchers to monitor the effect of flood management and study the relative importance of individual restoration measures, as well as the side effects of flood attenuation.
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| 4. |
- Rodríguez-González, Patricia M., et al.
(författare)
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Bringing the margin to the focus : 10 challenges for riparian vegetation science and management
- 2022
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Ingår i: WIREs Water. - : John Wiley & Sons. - 2049-1948. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- Riparian zones are the paragon of transitional ecosystems, providing critical habitat and ecosystem services that are especially threatened by global change. Following consultation with experts, 10 key challenges were identified to be addressed for riparian vegetation science and management improvement: (1) Create a distinct scientific community by establishing stronger bridges between disciplines; (2) Make riparian vegetation more visible and appreciated in society and policies; (3) Improve knowledge regarding biodiversity—ecosystem functioning links; (4) Manage spatial scale and context-based issues; (5) Improve knowledge on social dimensions of riparian vegetation; (6) Anticipate responses to emergent issues and future trajectories; (7) Enhance tools to quantify and prioritize ecosystem services; (8) Improve numerical modeling and simulation tools; (9) Calibrate methods and increase data availability for better indicators and monitoring practices and transferability; and (10) Undertake scientific validation of best management practices. These challenges are discussed and critiqued here, to guide future research into riparian vegetation.
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| 5. |
- Rysgaard, Søren, et al.
(författare)
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A mobile observatory powered by sun and wind for near real time measurements of atmospheric, glacial, terrestrial, limnic and coastal oceanic conditions in remote off-grid areas
- 2022
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Ingår i: HardwareX. - : Elsevier BV. - 2468-0672. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is rapidly altering the Arctic environment. Although long-term environmental observations have been made at a few locations in the Arctic, the incomplete coverage from ground stations is a main limitation to observations in these remote areas. Here we present a wind and sun powered multi-purpose mobile observatory (ARC-MO) that enables near real time measurements of air, ice, land, rivers, and marine parameters in remote off-grid areas. Two test units were constructed and placed in Northeast Greenland where they have collected data from cabled and wireless instruments deployed in the environment since late summer 2021. The two units can communicate locally via WiFi (units placed 25 km apart) and transmit near-real time data globally over satellite. Data are streamed live and accessible from (https://gios.org). The cost of one mobile observatory unit is c. 304.000€. These test units demonstrate the possibility for integrative and automated environmental data collection in remote coastal areas and could serve as models for a proposed global observatory system.
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| 6. |
- Urbanič, Gorazd, et al.
(författare)
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Riparian Zones—From Policy Neglected to Policy Integrated
- 2022
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Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- 1. Riparian zones are vital areas of interaction between land and rivers and are often degraded by several pressures such as urbanisation, intensive agriculture and river engineering works. 2. This policy brief provides five key policy messages and recommendations to be considered by policy-makers, scientists, managers, and stakeholders to enhance riparian zone management. 3. Adopting an integrated socio-economic and environmentally dynamic view will ensure the sustainable management of riparian zones. 4. In light of climate change, it is critically important to conserve and/or restore the ecological integrity of riparian zones. 5. European Union Directives and national-scale legislation and regulations need updating to ensure coordinated implementation of riparian zone-related policies. 6. Stakeholder knowledge exchange, policy co-creation and adaptive management are key to enhancing riparian zone functions.
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